Brake



July 25, 1939. G, McK. FlTTs 2,167,297

- BRAKE Filed Sept. 7, 1935 3 Sheets-Sheet 1 25, 1939. G. McK. FITTS BRAKE Filed Sept. '7, 1935 3 Sheets-Sheet 2 G. M K. FlTTS BRAKE July 25, 1939.

Filed'Sept. 7, 1935 3 Sheets-Sheet 3 Patented July 25, 1939 I UNITED; STATES PATENT OFFICE BRAKE George McKinley Fitts, Washin1gto'n, D. 0. Application September 7, 1935. Serial No. 39,652 6 Claims. (or; 188-78 This invention relates to brakes and-particularly to brakes of the internal expanding type. The present invention is an improvement over applicants prior application Serial No. 326,969,

5 filed December 19, 1928, and since issued as Patent No. 1,890,031.

It is an object of the invention to provide a brake of this type .in which the actuating means expands brake'shoes against a brake drum in such l= a manner. asto produce equal amount of'pressure at. all; points of. contact between'sai'd brake shoes andbrake drum.

It has been found that upon the expan'sionof' a brake shoe against the brake drum there is wrap- 16 ping of each of the shoesjagainst the drum'at a point farthest from its point of anchorage of the respective shoes. By wrapping, according to practical vernacular, it is meant that when the automobile wheel is turning the brake drum re- 20 volves and the brakeshoe is actuatedto contact the drums; and'the instantthe shoe makes con tact. with the drum there is a wrapping force between'the shoe andthe drum. In the present day brakes of this type, when expansion takes 25 effect it is well known. thatit starts at the point farthest from its anchoringpinva-nd the application of pressure between the shoe and-the drum is greatest at this point, andthe pressure gradually decreases asthe revolving drumlapproaohes. the

30. shoe in.proximity. of. the 'an'choringpin, i. e., the pressure of the shoe andthe. drum near the. anchor is muchless thanthepressure. at the instantfof expansion. This distorted application of pres.- sure has the effect of causing the drum to become 35 untrue or out of round, which upon continual wear between the drum and shoe-results in anundsirable vibration upon application ofthe brake,fthe common occurrence of grabbing and squealing. It has also been found that when. the drum be- 40 comes out of round, high and low spots occur which often cause the revolving. drum to lock against the shoe upon energizing.

Itis a further object of theinvention to provide a series of'floatin'g brakeshoes, each end of which 4.5 is provided with an adjustable tension spring-.vso as to keep .the shoe in linewith the circumference of the. brakedrum atall times.)

It is .afurtherobjectof theinvention to provide the brake shoe with an. elongated'endfie., from 50 the center of the pivot or anchorihg...pin the shoe has a longend anda short end; The long end; of the shoe islthepoint'at which thewrapping efiect would ordinarily take-place, b'utby so providing this elongated sectionth'ewrapping'force. between so the shoe andthe drum is'equalizdto allow the" shoe to be simultaneously expanded throughout, thus preventing any possibility of distortion between the drum and the shoe;

It is another object of the invention to provide shims at the ends of the shoesupports so as to 5 give further adjustability to the brake shoe upon being assembled, i. e., to prevent any possibility of variance in' clearance between the brake shoe and drum when being assembled.

'It is a further object of the invention to provide It is a further object of the invention to provide a plurality of V-type shoes which are so constructed at their ends to give a complete interlinking fit between the two shoes. The advantage of this type of shoe is to allow for pressure at all points on the inner circumference of the brake 0 drum, 1. e., the pressure exerted'between the ends ofjthe brake shoes is equally as great as on the remaining portion of the shoe.

Further objects of the invention will appear from the following description taken in connection with the accompanying drawings which illustratea perferred embodiment of theinvention, and in which:

Fig. 1 is a vertical section through the brake mechanism, the section being taken on line l-l of Fig. 2 in a plane at right angles to the brake drum.

Fig. 2 is avertical sectional view of Fig. 1, taken through Fig. 1.

Fig. 3 is a side view of one form of the brake shoe.

' Fig. 4 is a rear view of Fig. 3 showing the specificV-type shoe.

Fig. 5 is cross-sectional View of the shoe taken on line 22 'of Fig. 4.

Fig. 6 is a modified quarter-section of Fig. 1, showing the modified flat-type shoe.

Fig. '7 is top view of the shoes employed in Figs. 1-5, showing the V-shaped fitting ends.

Fig. 8 is a modification showing a two shoe flat type hydraulically actuated.

Referring in detail to the accompanying drawings, the invention includes a split brake drum I having screws 2 fastening it to the other druml Within the drum land the drum support3 are 507 serving to givethe. sliding movement of'the shoe supports 4 and 5. Screws 9 are provided to hold the plate ID to the bolt 1, said plate in turn assisting in the guiding of the shoe supports.

Within each slot 6 is located a coil spring H which bears at one end against the shoe support and the other end against the anchor bolt 1. The springs ll are under compression and serve as retraction springs, i. e., to urge the shoe supports 4 and constantly toward each other and away from the brake drum. The advantage of this particular method of anchoring the 'shoe supports will be referred to later in this disclosure.

Coil springs l2 and I2 are adapted to fit in apertures and also serve to urge the supports 3 and 5 constantly toward each other; The ends of the springs are fitted in the apertures l3 to give a direct pull on the supports and eliminates any possibility of the supports swerving upon expansion.

Anchoring pins l5 serve as pivots for the brake shoes I 2 carrying brake lining i6, said shoes adapted to be brought into contact with the drum I when the shoe supports are expanded for braking action, as hereinafter described.

The shoe M, as. clearly shown in Figs. 1 and 3, is composed of a long end H and a short end I8 1. e. if a center line is drawn through the anchoring pin i5 of the brake shoe which is perpendicular to outer circumference of the brake shoe or at right angles to the longitudinal axes of the pin, the end ll of the shoe is longer from .said center line than the opposite end of the shoe l8. See Figure 3. At each end of the brake shoe coil compression springs. iii are provided, which are adapted to bear at one end against the brake shoe and at the other end against the adjusting bolt 2e threaded into the shoe support t. The bolt 2i] carries a lock nut 2i so upon assembling the mechanism the shoe must be in perfect conformity with the drum and if any variance in clearance is present at any point between the shoe and the drum, the bolt 23 can be adjusted to allow for such clearance, and then locked by the nut 2i and thus give a uniform assembly throughout. The springs l9 also serve as equalizing means and aid in insuring that the pressure at all points along the brake shoe will be equal during its braking action against the drum.

The long end i! of the V-type shoe l t equalizes the wrapping force of the brake shoe upon expansion in that when the shoe it expands from the pivot point of the shoe, the long end I! balances the shoe by preventing the shoe from turning in a direction opposite to the direction of the arrow, as shown in Fig. l, i. e., prevents the shoe from turning in an anticlockwise direction. The eflect of this balancing is to equalize the pressure of the shoe at all points and thus give a perfect simultaneous expansion. Consequently by this simultaneous expansion there is an even and uniform wear on the brake lining overall. This can be readily seen from an application of the forces upon expansion. The long end I? equalizes the overrunning torque and the reactive forces at the anchoring point l5.

As. clearly shown in Figs. 1 to 5 inclusive, and in Fig, 7, the present invention involves the use of V-type shoes in lieu of the ordinary fiat type, whereas the shoe M has two perpendicular sides. In Fig. '7 the ends of the shoe M are shown in a V-shape interfitting into each other, the V- shapedend 23 adapted to conform to the cut out washer plate 29.

I3 for connecting the shoe supports V-shaped portion 24 with the sections 25 and 26 likewise conforming. The advantage of this con struction has been referred to above.

From the above it can be seen this equalization of forces, which results in a uniform wear on the lining, will prevent wrapping and the detrimental results which occur from it.

Between the adjacent ends of the semi-circular shoe supports 4 and 5 a double acting cam 27 is provided, which is pivotally mounted by a threaded bolt 28 for partial rotation on the brake drum support 3 and protected from slipping off by a Each cam 21 is provided with an actuating lever 30 and the levers are connected by a link 3| so that upon operation of one a of the cams the other cam will also be actuated in unison therewith. The cam 21 is actuated by a link and lever from the foot brake pedal or hand lever not shown.

On each adjacent end of the supports 4 and 5 are provided shims 32 held by screws 33. These shims are important in that they allow for adjustability of the supports t and 5 and can be increased to take any slight wear on the cam 2'1.

Fig. 6 shows a modification of applicants device using the ordinary fiat type shoe, in which li is the elongated portion of the shoe. The principle of operation is identical as for that of a V-type shoe, as shown in the preferred embodiment.

Fig. 8 is another modification of the device showing the single brake shoe I4 mounted on each semi-circular member 4 and 5 constituting a two shoe type of brake. This modification discloses the use of an hydraulic cylinder 48 and piston 4| to actuate the lever 42, arm '33 and lever 44 which in turn drives the cams 48 anchored by pins 41 to simultaneously expand the shoe supports 4' and5 which are anchored at 50. The brake shoes M are shown pivoted at l5 and the operation is identical with that disclosed for the preferred embodiment.

The invention operates as follows: Upon pressure being exerted from the brake pedal (not shown) the cams 21 are actuated to expand the semi-circular members 4 and 5 diametrically toward the drum l,which in turn expands the brake shoes [4 and the brake lining l6 against the brake drum. The slot 6, screw 9, and spring II serve to guide the semi-circular members in a direct path of expansion. Upon coming in contact with the drum, the elongated end of the shoe equalizes the pressure between the shoe and the drum, the springs l9 assisting in equalizing the pressure and thus effecting a simultaneously expanded shoe.

I claim: 7

V 1. A brake comprising a drum, brake shoe carriers, V-type brake shoes, pivotally mounted on said carriers, said shoes having V-shaped ends interfitting into each other. 2. A brake comprising a drum, brake shoe carriers, pivoted brake shoes on said carriers, one end of each shoe from the center line of the pivot being longer than the other, said shoes having V-shaped ends interfitting into each other.

3. In combination a brake drum, a plurality of brake shoes associated with said drum, said shoes having V-shaped ends interfitting into each other.

4. A pivoted V-type brake shoe having V-shaped ends, one end 'of the shoe being longer than the other relative to a center line of the pivot.

5. A brake comprising a drum, a brake support, a pair of brake shoe carriers, guide means on said supports, springs bearing on said guide means and said carriers, springs connecting said carriers urging them toward each other, a plurality of pivoted brake shoes mounted on each of said carriers, each shoe having one end from the center of the pivot longer than the opposite end, said longer end of the shoes positioned adjacent'the opposite shorter end of the adjoining shoe, and a pair of equalizing springs between the shoe and carriers, and means for actuating said carriers toward the brake drum.

6. In combination a brake having a V-shaped brake drum, said drum being split into two sections, a plurality of pivoted brake shoes, having elongated ends relative to the center line of the pivot the elongated end of each shoe positioned adjacent the non-elongated end of the adjoining shoe.

GEORGE MCKINLEY FITTS. 

